1. Field of the Invention
The invention relates to power engineering and, in particular, to the methods and devices for conversion of the continuous medium flow energy into mechanical energy.
This invention may be used in wind and hydraulic driven power engineering in various hydraulic and gas dynamic systems, for instance, when the motion of liquids, gas, two-phase or multicomponent media is used for mechanical energy generation.
The invention can be most successfully used in wind-driven electric power plants, in hydroelectric power plants, arranged in river beds (without dams), in tide-driven hydroelectric power plants, as well as when the energy of thermoinduced flows is utilised including sun-heated thermoinduced flows.
2. Description of Related Art
Known are methods of concentration of the wind flow power by placing into the flow devices in the form of a convergent-divergent reflector arranged coaxially with the direction of flow of the wind to increase its velocity and hence the power of the flow directed onto the power generating units of the above indicated electric plants.
What is common for such methods is that the profitability of their utilisation in wind-driven power generating systems of different type depends on the average velocity V of the flow.
For wind-driven electric power plants this velocity is V=8 to 12 m/s. In addition, during the motion of the wind along the path of the device realising this or that energy conversion method as well as in the course of the interaction between the continuous medium flow and the elements of the said device, harmful secondary flows in the shape of vortices are generated, and some energy of the flow is spent on their formation; due to this fact, the flow is subject to an additional dynamic resistance which reduces the efficiency of conversion of its energy.
In other words, since harmful secondary vortex flows are generated in the flow against the background of the main flow during the interaction between the flow and the elements of the power generating plant or when the flow is moving along the path of the device, the efficiency of conversion was limited by the loss of energy on the formation of the vortices.
There is a prior art method for the conversion of the continuous medium flow energy into mechanical energy according to which a rotational moment is imparted to the flow, and this moment is directed into the inlet chamber and into a system of channels; a reduced pressure is created in the flow and this ensures an inflow of the medium from the external space and a concentration of the power in the formed flow; then the flow energy accumulated in this way is converted by means of the rotary-action mechanism (Ragwalla, A. A., Hsu, C. T., “Power Coefficient of Tornado-Type Wind Turbines”. Journal Energy, 1983, V. 7, No. 66, p. 735-737; Hsu, Ñ. Ò., Ide, H., “Performance of Tornado-Type Wind Turbines with Radial Supply”. Journal Energy, V. 7, No. 6, 1983, p. 452-453).
The devices which realise this method are called TWES (Tornado Wind Energy Systems) and they essentially are towers inside of which a tornado-like vortex flow is generated. As it was already mentioned, this flow originates due to the inflow of air inside the tower through one or a multiplicity of slots forming an arbitrary, but permanent for the given structure, angle with the local radius of the tower.
The slots in the tower are open on the windward side and closed on the leeward side. Upon passing through these slots the wind acquires a tangential velocity component, and this involves the origination of a vortex flow inside the tower. A reduced pressure zone is formed in the core of such flow, and this results in the suction of additional masses of air inside the tower through the tower bottom, installed on a special device designed for creating a draught.
The authors of the works cited and other researchers (see, for instance, the works of So, R. M. C., “On Vortex Wind Power”. Journal of Fluids Engineering, 1978, V. 100, p. 79-82) were guided by a wrong conception that the velocity field in the TWES is characterised by a distribution which is a characteristic of the Burgers vortex (Burgers, J. M., “A Mathematical Model Illustrating the Theory of Turbulence”. Advanced Appl. Median., 1948, V. 1, p. 157-199). However, realisation of this method in the corresponding devices testifies to rather large losses, caused by the above-described absence of conditions, which are intended to ensure smooth joining of the stream-lines in the jets, flowing through the slots into the tornado tower, with the stream-lines in the formed tornado-like flow.
The disadvantage of the given energy conversion method and of the devices, based on this method, is that in this case the motion of the flow in the form of separate jets along the channels or volumes, into which this flow is directed, is characterised by nonstationary stream-lines, by their sharp bends and, as a consequence, by the formation of harmful secondary vortex flows involving energy losses by the flows and a low degree of efficiency of the device, by means of which the said method is realised.
From the hydrodynamic point of view the employed flow and the transferred continuous medium flow are forced to form in their inside not only those stream-lines, which are required for the realisation of the method, but also a large number of nonstationary parasite trajectories. This results from the disagreement in the formation of the flow according to the said method accompanied by the natural conditions of smooth vortex-free flow of continuous media, and the formation of tornadoes under natural conditions may serve as an example.
There is another prior art method of energy conversion of a continuous medium flow comprising that the flow to be converted is directed into an internal axissymmetric volume along two systems of trajectories converging towards the axis of symmetry of this volume; the first of the said systems forms a vortex flow just in front of the zone of conversion of the rotational moment and mechanical energy, ensures concentration of the mechanical energy and rotational moment in the axissymmetric volume, as well as the further conversion of the mechanical energy and rotational moment in the same volume, whereas the second system of trajectories forms a flow with a reduced pressure, the said pressure reduction ensuring evacuation of the continuous medium, which flows out of the mechanical energy and rotational moment conversion zone; the first system of trajectories fills first the space area which is limited by the two surfaces of revolution and then assumes the form of helices.
A device is known for conversion of the energy of natural flows; this device includes a converging chamber, two systems of channels arranged symmetrically with regard to the central axis of the device, the first of the systems being provided with axes in the form of helices, a turbine with a fairing, smoothly conjugated to the central internal fairing, an electric generator connected to the turbine by means of the central shaft, passing through the central fairing, and a supporting structure.
The above method and device for its realisation have the following disadvantages: there is no axial swirling in the first system of trajectories and, therefore, the first system creates a rather weak reduced pressure in the area, delivered to which the flow is running out of the energy conversion zone; there is no description of the shape of the first system of channels, which could ensure high efficiency of energy conversion of the continuous medium flow in the said device.
In RU 20 59 881 G. I. Kiknadze, I. A. Gachechiladze and V. G. Oleinikov are proposing a method of conversion of continuous medium flow energy and a device for a realisation thereof wherein generation of harmful secondary vortices is reduced to a maximum to avoid any energy losses based on these harmful secondary vortices. In general it is proposed to organize a flow or flows of the streaming medium in a manner avoiding generation of any additional vortices not contributing to a conversion of energy to a maximum extend.